The invention relates to a novel and unique memory device for directly and continuously storing information relative to physical phenomena, to physical and chemical variables in an industrial process, and it also relates to a method of using such memory for data storage, for gas or liquid sampling, for sensing and recording process control variables, for monitoring and controlling an industrial process. The invention further relates to monitoring, sensing and control apparatus making use of such memory device and method.
The invention relates more particularly to memory devices including as storing element material possessing magnetic domains.
Memory devices are classified as non-destructive and as destructive. Non-destructive memory devices afford the possibility to write and read then erase and again write information data. The destructive type can permit repetitive reading, but the information is permanently stored in the storing medium. A read only memory is typical of this second type.
Magnetic memory devices generally take advantage of the fixed orientation taken by magnetic moments under the effect of an external magnetic field, thus creating a magnetic condition in the material which can be read at a later time. In that sense, a magnetic memory device, in the prior art, is always non-destructive since a change of orientation of magnetic moments does not affect the fundamental structure of the material.
Read-only memory devices, nevertheless, have been manufactured in the past with such non-destructive memories by combining memory elements and by so separating electrically the zones of exposure to external influence that changes effected in one zone become irreversible in relation to another zone.
A common type of magnetic memory device is the magnetic tape used in sound recording or as an integral part of a computer. The magnetic tape in sound recording is not exposed directly to the effects of the acoustic waves. A transducer device is necessary in order to convert the acoustic wave into an electrical signal used to impress on the tape a corresponding magnetic field altering the magnetic state of the tape. With the electronic computer, data information is stored into the tape at the input side by electromechanical means, which also are in substance a transducer.
Attempts have been made already in order to apply the magnetic storing quality of magnetic materials to the recording and monitoring of physical phenomena, and more particularly as a means for on-line chemical analysis of chemical reactions. For instance, in the U.S. Pat. No. 3,868,059 issued Feb. 25, 1975 to W. M. Hickam et al, assigned to the same assignee as the assignee of the present application, and entitled "Magnetic Bridge-Type Meter For Magnetically Permeable Particulate Matter", is described apparatus for the detection of fly ash emitted in the exhaust of a coal-fired furnace. The fly ash is admitted into the air gap of a permanent magnet associated with a magnetic bridge circuit and the change in inductance, thus caused, is detected as an indication of the operative conditions of the furnace. Therefore, the Hickam patent shows an apparatus having inherent magnetic characteristics which is directly exposed to an external physical phenomenon to be sensed and monitored, with the altered magnetic characteristics being used for detection and monitoring of the external physical phenomenon.
In the same vein, it is known from a paper presented at a Conference on Magnetic Materials held at Philadelphia in December 1975, entitled "Magnetic Gas Sensor" by Martin Rayl, Peter J. Woytowicz and Harold D. Hanson, to expose the core of an electromagnetic coil to oxidation-reduction reaction by gases, so that chemical changes occur in the material and the resulting change in inductance is measured as an indication of the presence of the gas.
Still, the prior art does not fulfill all the major needs of the industry regarding the acquisition of data relative to physical and chemical processes, or the determination of the chemical composition of gases, liquids, and solids. An absolute compositional analysis or merely the compositional variance from one acceptable reference standard may be required. The means for achieving compositional analysis are many and varied. They include the older wet chemical methods and numerous instrumental methods based on various scientific principles. In general, the analysis as currently practiced consists of five primary stages: (1) Sampling and sample conditioning, (2) Processing of sample through a selected analytical method, (3) Data readout and reduction, (4) Data storage, and (5) Compositional information feedback. Much has been said about these stages, their operative modes, their limitations, the possible applications, the problems of implementation, personnel requirements, and costs. For example, ASTM has published approved procedures for achieving compositional analysis of many materials. Various analytical instruments for laboratory use have been manufactured and extensively marketed to meet the needs for compositional analysis of materials. In many applications the laboratory instruments have been found inappropriate and insufficient, or too expensive in terms of initial cost and personnel cost. Their main drawback lies in the chemical uncertainties introduced by sampling, sample conditioning, and sample storage. Some instruments are capable of operating only on samples brought to ambient temperature and atmospheric pressure. Others require elaborate and variable data readout systems with personnel requirements for data reduction and storage. Most of these instruments do not lend themselves to automatic feedback control, a highly desirable feature for manufacture and manufacturing processes.
The present invention is a novel approach to acquiring and utilizing chemical and physical information on materials, industrial and chemical processing of materials, physical phenomena.